diff --git a/core/admin/mailu/internal/views/postfix.py b/core/admin/mailu/internal/views/postfix.py
index f0fbaa5d..894532a3 100644
--- a/core/admin/mailu/internal/views/postfix.py
+++ b/core/admin/mailu/internal/views/postfix.py
@@ -27,7 +27,7 @@ def postfix_alias_map(alias):
 
 @internal.route("/postfix/transport/<email>")
 def postfix_transport(email):
-    localpart, domain = models.Email.resolve_domain(email)
+    localpart, domain_name = models.Email.resolve_domain(email)
     relay = models.Relay.query.get(domain_name) or flask.abort(404)
     return flask.jsonify("smtp:[{}]".format(relay.smtp))